This invention relates to pipe or tubing assemblies. More particularly, the invention relates to an assembly having un-coated components connected to galvanized or otherwise coated steel pipe using flanged connections. The invention encompasses a valve and pipe assembly that includes an un-flanged valve connected between two flanged pipe components. The invention also encompasses a method for manufacturing a valve and pipe assembly made of coated and un-coated components.
Valve and pipe assemblies are used in many applications, and particularly in industrial applications. A manifold is a common example of a valve and pipe assembly having wide industrial application. Manifolds are made up of a number of pipe segments interconnected with valves which are used to control the direction or route of fluid flow through the various pipe segments. For example, a manifold may include two fluid input points and two fluid output points. The valves in this example manifold may be arranged to selectively direct fluid from either input to either output, combine two input streams and direct the mixed stream to a single output, split a single input stream into two output streams, or completely block flow between either input and either output.
Various types of connections may be used to interconnect the pipe segments and valves in a manifold or other valve and pipe assembly. For example, a valve in a valve and pipe assembly may be connected to the adjacent pipe segments through threaded connections or flanged connections. A threaded connection uses threads on each end of the valve and on each pipe end. Making the connection requires rotating the valve with respect to the pipe segments or rotating the pipe segments with respect to the valve in order to thread the valve and pipe segments together. In a flanged connection between a valve and two pipe segments, the valve includes a flange at each end and each pipe segment end also includes a corresponding flange. The flange connection is made by aligning each flange on the valve with a different pipe flange and then bolting the flanges together, usually with an O-ring sealing element sandwiched between the opposing flange faces. Alternatively to threading or flanging a valve between two pipe segments, a valve may also be welded between two pipe segments to form a permanent connection. Welding requires that the valve and pipe segments meet or fit together in a position suitable for accepting a weld.
In many industrial applications, valve and pipe assemblies are used in corrosive environments. Manifolds and other pipe assemblies used in these corrosive environments must be manufactured from corrosive resistant materials or protected with corrosive resistant coatings. For example, both the pipe segments and valves in a valve and pipe assembly may be made of corrosive resistant materials such as stainless steel. Alternatively to forming the various valves and pipes in an assembly from corrosive resistant materials, the various components may be made of galvanized or coated carbon steel. Galvanized carbon steel has a protective outer layer of zinc which is deposited on the steel in a separate galvanization process after the steel is formed. In addition to galvanizing, other protective coatings may be used to protect carbon steel used in corrosive environments.
The choice of connections and choice of materials used in a valve and pipe assembly will depend upon a number of factors including the pressures to which the assembly will be subjected and the environment in which the assembly will be used. Corrosion resistant components such as stainless steel or galvanized steel must be used where the assembly will be subjected to corrosive environments. Flanged or welded connections are generally preferred for high pressure applications, and may be required by industry standards even for low pressure applications. However, welded connections should not be used for previously coated steel components because welding destroys the coating in the area of the weld and leaves the weld joint unprotected. Also, the heat of welding may release dangerous gases from some coatings, especially the zinc coatings of galvanized components.
An entire valve and pipe assembly may be made from flanged stainless steel components to accommodate high pressures or industry standards and to withstand corrosive environments. However, it is desirable to avoid using stainless steel components whenever possible in order to avoid the expense of stainless steel components. Using coated carbon steel pipe segments in a valve and pipe assembly such as a manifold may greatly reduce the cost of the manifold as compared to using stainless steel pipe segments. The cost of the assembly could be reduced further by eliminating stainless steel or carbon steel valves and instead using less expensive valve components.
Bronze valves are a desirable alternative to steel valves in many applications because bronze valves are much less costly than both carbon steel and stainless steel valves and because bronze valves provide excellent resistance to corrosion. Prior to the present invention, however, bronze valves posed problems in applications where welded or flanged connections were required. Bronze valves are typically manufactured with threaded connections and not with flanges. Thus, a bronze valve would have to be welded to the pipe segments or be specially manufactured with flanges. Having bronze valves specially manufactured would increase the cost of the valves and defeat the primary purpose of using bronze valves over steel valves. Also, welding the bronze valves in place is not possible using conventional welding techniques. Therefore, it has not been practical to use bronze valves and steel pipe to form a flanged or welded valve and pipe assembly, especially where the assembly is to be used in corrosive environments requiring any carbon steel components to be durably coated.
It is an object of the invention to provide a valve and pipe assembly which overcomes the above-described problems associated with valve and pipe assemblies which are subjected to corrosive environments and require flanged or welded connections. More particularly, it is an object of the invention to provide a valve and pipe assembly having an unflanged valve which is connected in a line of flanged pipe, especially flanged pipe which is pre-coated. It is another object of the invention to provide a method for connecting an unflanged valve with the coated pipe.
A valve and pipe assembly according to the invention includes a valve, a first pipe component, and a second pipe component. Each pipe component includes a length of pipe having a flange secured at one end. Rather than including flanges, the valve includes a first valve sealing surface at a first end and a second valve sealing surface at a second end. The valve is positioned between the two pipe components with the first valve sealing surface facing the flange associated with one pipe component and the second valve sealing surface facing the flange associated the other pipe component. A flange connector arrangement, preferably comprising a number of bolts (two or more) extending between the two pipe component flanges, connects the two flanges together with the valve component sandwiched in between. This connection between the two pipe component flanges produces two sealing connections. A first sealing connection is formed between the first valve sealing surface and the flange that it abuts, and a second sealing connection is formed between the second valve sealing surface and the flange that it abuts.
Perhaps the most important benefit of the valve and pipe assembly according to the present invention is that the assembly allows an inexpensive, unflanged bronze valve to be connected to two flanged pipe segments that are protected from corrosion with a durable coating such as galvanizing. Any welding required to produce the two pipe components may be performed before the pipe is coated. Thus, the coating on the pipe components and their associated flanges remains substantially intact to protect the underlying steel. The valve and pipe assembly is therefore well suited for use in corrosive environments and can be used in place of the much more expensive assemblies using all stainless steel components or mixtures of stainless steel components and galvanized steel components.
Where the flanged pipe segments require a coating for corrosion protection, the invention is particularly suited for situations in which the flanged pipe segments are coated with a material or in a process incompatible with the valve. This is the case where the valve is a bronze valve and the flanged pipe segments must be galvanized or coated in some other process that subjects the material to harsh chemicals and/or high temperatures. In these situations, it is not possible to simply make the assembly and apply the coating to the entire assembly. Rather, the parts to be coated must be coated prior to connecting the assembly. The preferred manufacturing process, which includes coating the flanged pipe segments prior to making the assembly, will be discussed in detail with reference to FIGS. 4-9 below.
The valve component used in the a valve and pipe assembly according to the invention may include positioning features on its exterior surface which may cooperate with one or more of the flange bolts to limit any rotation of the valve with respect to the two pipe components. The required cooperation may be achieved by using a minimum clearance between the flange bolts and the outside diameter of the pipe of the two pipe components. This minimum clearance places the flange bolts close to the valve body in position to contact the positioning features and thus prevent the valve body from rotating with respect to the two pipe components.
In the preferred form of the invention, each pipe component includes an alignment tube extending past the sealing face of the respective flange. These alignment tubes are inserted into the bore on either end of the valve and ensure that the valve is in the proper position to produce the sealing connections required against the respective pipe flanges at each end of the valve. The base of each alignment tube also preferably helps form an area for receiving an O-ring which helps facilitate the seal at each end of the valve body.
The method of manufacturing a valve and pipe assembly according to the invention includes welding a first flange to a first pipe to form a first component and welding second flange to a second pipe to form a second component. After coating the first and second components, the method includes machining flange sealing surfaces on each flange so that a good sealing connection can be made with the valve sealing surfaces. Once the flange sealing surfaces are machined, the method includes aligning the valve in a connected position between the first flange sealing surface and the second flange sealing surface and then connecting the two flanges together to produce the desired sealing connections between the sealing surfaces at each end of the valve and the respective pipe flanges. These seals may result from the direct contact between the valve material and the flange material or through an intermediate material such as an O-ring positioned between the respective valve sealing surface and flange sealing surface.
The preferred form of the invention includes welding the flanges on the respective pipes so that the bolt holes for receiving the flange connecting bolts can reside as close as possible to the outside surface of the pipe. This close spacing between the flange bolt holes and the pipe outside surface helps facilitate the desired cooperation between the flange bolts and positioning feature on the valve body to prevent the valve from rotating with respect to the pipe components. The preferred flange welding step comprises welding each flange to the respective pipe only on the side of the flange facing a near end of the pipe, that is, the side which will face the valve body when the assembly is connected. The welding fills a chamfer area in order to provide sufficient strength in the pipe to flange weld.
In order to produce the alignment tubes the pipe flanges are preferably welded to the respective pipe segment at a point somewhat removed from the end of the pipe so as to leave a pipe extension protruding from the flange. After coating these unmachined pipe components, the method preferably includes turning down the outside of each pipe extension to form the alignment tubes and removing coating from a portion of the flange facing the near end of the respective pipe. This machined portion of the respective flange face comprises the flange sealing surface which cooperates with the respective valve sealing surface to form the desired sealing connection, with or without an O-ring.
These and other objects, advantages, and features of the invention will be apparent from the following description of the preferred embodiment, when considered with the accompanying drawings.